I can confirm that MIDI sync works using a standard arduinoboy set to LSDJ slave mode. You have to find the correct overflow timer increment to match your beat. I found that multiples of 12 produce arpeggios in sync with the beat pulses, but of course fun stuff can be done by using uneven ratios.
Hey good testing. 
Cheers. Yes a midi clock is much slower than the internal clock. The internal interrupt is clocked at 4096Hz and a midi clock at 24 ticks per beat. Setting it to 12 should be playing at double speed, I think anyway.
The only issue I have so far is that,while chord goes along well with the incoming sync, it will aways be a bit shifted. Even if you try hard pressing the buttons when you hear a beat, it will always be a bit off. I think chord should reset to the sync signal from time to time to keep everything "in grid".
Good point. Chord has only been reseting the timer on changing the tempo. I have uploaded a new build that restarts the timer on the first note, if the left button timer is zero. I didn't bother to bump the version number though. And I will do some thinking on how to best reset the timer during playing...
Also I noticed that sometimes it works nicely with the sync and sometimes it goes in "Steve Reich Mode" i.e. it will slowly shift out of phase, even with the correct settings, can't say why but will test further.
Hmm, I have double checked the code and I can't see anything that would cause this behaviour. My guess is that arduino boy struggles to keep up with the tempo you are playing at. What you could try is halving the tempo and change the overflow buffer to compensate. But I am not sure, it might not be the problem.
Cheers again for the feedback.
ERik
